Life Support

Human space exploration is a critical aspect of space sciences. Although robotic probes are invaluable for preliminary studies or high-risk environments, humans are able to solve problems, improvise, and make discoveries that are not programmed into a probe's software. Keeping astronauts safe and healthy while in space is a major concern. Non-astronauts take for granted many of the life support concerns that astronauts must consciously address to ensure their mission's success. Variables include gas requirements, temperature, gravity, radiation, and pressure. Waste products must be carefully monitored, and disposal or recycling must be planned. When astronauts leave Earth, many plans, procedures, and backup systems are in place for their comfort and survival.

Temperature

During a space mission, astronauts and their spacecraft are exposed to temperature extremes on both ends of the scale. On the Moon, for example, when the Sun is up, the surface temperature can go as high as 243°F (117°C) but at night it can drop to -272°F (-169°C). This was a major concern for the Apollo Moon missions.

The vacuum of space is extremely cold and deadly to unprotected human life. However, the heat felt during liftoff and re-entry through the atmosphere is intensely hot. Engineers must design space suits that keep astronauts warm when they embark on space walks in the extreme cold of space. They must also design heat shielding for the space shuttle that will withstand the high temperatures of re-entry into Earth's atmosphere. For example, after the shuttle has entered orbit, the cargo bay doors open to help release much of the pent-up heat created during liftoff and ascent. Conversely, the shuttle must be pointed at a appropriate angle and rotation to ensure that the heat of re-entry is distributed properly against specially reinforced, heat-resistant panels. During re-entry, the space shuttle will encounter incredibly hot temperatures—up to 3,000°F. This requires the shuttle to be equipped for the temperature extremes.

Gravity and Microgravity

During liftoff, the effects of gravity on the human body are intense and cause physical discomfort. Astronauts are tested in simulators to ensure they can survive the gravitational effects of space shuttle liftoff, which are up to three times that of Earth gravity.

Once in space, astronauts must adapt to microgravity, a nearly weightless environment. Human bodies are accustomed to the amount of gravity experienced on Earth, where muscles and bones are always competing with gravity. But in space, astronauts lose bone and muscle mass. Their hearts do not have to beat as hard or as fast to make blood pump through the body. Despite a rigorous exercise schedule while in space, nearly all astronauts exhibit muscle and bone deterioration after spaceflights of significant duration.

Other Survival Concerns

Humans bodies take in food, water, and oxygen necessary for life, and then produce wastes as liquids, solids, and carbon dioxide. Space missions must ensure an adequate supply of life-sustaining resources for the journey, as well as a safe way of disposing of waste products. Recycling is important in space, and both technological and biological equipment are used. Many different ways of waste product disposal have been used and or studied by NASA. These methods include space jettison, plant fertilizers, and technology that filters and cleans the waste to allow useful materials to be reused.

Extra vehicular activity (EVA) suits, protect astronauts in the vacuum of space. These suits protect against extreme cold, radiation, and help recycle carbon dioxide into oxygen. However, just as the space shuttle has its limitations, these suits do as well. Their life support systems can be overwhelmed, requiring that they be used for only short periods of time, such as space walks. During space walks, MMUs (Manned Maneuvering Units) have been used as a means of moving small distances. The MMUs are similar to jetpacks for the astronauts. They allow small bursts of propulsion thrusters to be fired from the pack, allowing astronauts to change their direction and momentum.

One commonly forgotten life support concern is the energy required for all of the spacecraft's equipment. The space shuttle must have failsafes to ensure that there will be enough energy for the onboard computer systems, just as there must be sufficient fuel. These energy sources are as important as any other because without them, the mission would not be feasible. Extensive research is underway to try and use new, cheaper fuels in future human space exploration missions.

SEE ALSO LIVING IN SPACE (VOLUME 3); MANNED MANEUVERING UNIT (VOLUME 3); SPACE WALKS (VOLUME 3).

Craig Samuels

Bibliography

Davis, Amanda. Exploring Space: Space Stations—Living and Working in Space. New York: Rosen Publishing, 1998.

Sulzman, Frank M., and Albert M. Genin, eds. Space Biology and Medicine, Vol. 2: Life Support and Habitability. Reston, VA: American Institute of Aeronautics and Astronautics, 1994.

Internet Resources

Advanced Life Support and Gravitational Biology at Kennedy Space Center. NASA Kennedy Space Center. <http://bioscience.ksc.nasa.gov/oldals/>.

Advance Life Support: NASA Johnson Space Center. NASA Johnson Space Center.<http://advlifesupport.jsc.nasa.gov>.

Lifting Bodies See Hypersonic Programs (Volume 3).